Percentage change in resistivity of a material or component resulting from a unit change in temperature, or the temperature coefficient of resistance (TCR), is a figure of merit for thermal sensing applications, and in thin film bolometers based on film temperature the responsivity is found to be directly proportional to the TCR. To achieve the best possible bolometric responsivity, different material platforms have been explored, and in research carbon nanotube films and carbon nanotube-polymer nanocomposites have been proposed for bolometric infrared detection based on their characteristics of high optical absorbance, low thermal mass, high strength and elasticity, light weight and potentially low cost synthesis processing. Aliev., Infrared Physics & Technology, 51: 541-54, 2008; Itkis et al., Science, 312:413-416, 2006; Lu et al., Journal of Applied Physics, 108:084305-084310; Tarasov et al., Applied Physics Letters, 90: 163503-163506; Itkis et al., Nano Letters, 2:155-159, 2002; Kataura et al., Synthetic Metals, 103:2555-2558, 1999; Kymakis et al., Synthetic Metals, 127:59-62, 2002, Dalton et al., Synthetic Metals, 102:1176-1177, 1999.
However, the room temperature TCR values for carbon nanotubes and carbon nanotube-polymer nanocomposites have not surpassed the −0.5%/° C. mark [negative 0.5 percent per ° C.]. Aliev, Ibid.; Itkis et al., Ibid.; Jakubinek et al., Applied Physics Letters, 96: 083105-083108, 2010; Lu et al., Applied Physics Letters, 93:213101-213104, 2008; Tarasov et al., Ibid. These low TCR values place stringent requirements on device engineering and thermal management to achieve adequate responsivities, and to offset potential cost and weight benefits offered by carbon nanotube-based platforms. Reports describing carbon nanotube film bolometers show only adequate performances at pressures in the milliTorr range with substantial or total loss of responsivity at room pressure, at which thermal coupling of the low mass film with its surroundings is much greater.
There is a need for devices and methods for configuring a nanoparticle sensing element to result in high TCR, such that enhanced uncooled IR bolometric detection can be readily observed in its as-is thin-film form, before applying any packaging or thermal engineering strategies.